The present invention, in some embodiments thereof, relates to pharmaceuticals, and more particularly, but not exclusively, to a molecular structure that acts as a multiple-drug delivery vehicle, and to uses thereof.
Delivery of drugs to medicinally targeted loci in a living organism has been for decades a challenging mission of many medical and chemical research endeavors. An even more challenging task is the delivery of more than one type of drug to a target site, while another is the concerted and controlled targeted release of multiple drugs from a single carrier molecule. For example, targeting drugs by conjugation to a targeting moiety (also referred to herein interchangeably as a “carrier molecule”, “carrier” and “biomolecular carrier”) having a high affinity to specific receptors on cancer cells provides a solution for two major problems in anticancer therapy: the lack of target cell specificity of most anticancer drugs and improvement of their toxicology.
Attempts have been made to employ complex molecular structures to targeting moieties, mainly encapsulating structures, as well polymeric and dendrimers carrier structures. However, these attempts were aimed at, or generally achieved molecular structures that were capable of delivering either one type of drug in multiple copies, or release the drugs under one type of physiological condition and/or rate of release. Over the past decades, carrier-drug conjugates have been developed to target cell delivery of potent anticancer drugs with the aim of eliminating the morbidity-causing non-specific side effects common to conventional chemotherapy. Typically, the carriers are macromolecules such as monoclonal antibodies and other proteins, or smaller molecular carriers like polynucleotide segments and peptides. Despite advances in these areas, the carrier-drug conjugates reported so far are limited to carry one drug type, although drug conjugation chemistry is well elaborated.
Several recent publications presented biologically active peptide-drug conjugates, manifesting improvement of the drug-like features of the linked drugs. It has been demonstrated that bioconjugates containing the GnRH-III peptide can be used as a targeting moiety [Leurs, U. et al., Peptide Sci, 2011, 98, 1-10], and the chemotherapeutic agent daunorubicin has been demonstrated as drug delivery systems for targeted cancer chemotherapy [Organ, E. et al., Amino Acids, 2010, DOI: 10.1007/s00726-010-0766-1; and Szabo, I. et al., Bioconjug Chem, 2009, 20, 656-665]. Selective accumulation and prolonged retention of the RGD analog c(RGDfK), linked to fluorescent bacteriochlorophyll derivative, has been reported in the tumor necrotic domain in MDA-MB-231-RFP bearing mice, which enabled early detection of tumor growth and foster prognosis and the development of novel modes of treatment [Goldshaid, L. et al., Breast Cancer Res, 2010, 12, R29].
The most clinically studied peptide-drug-conjugate is GRN1005, an angiopeptin-2-paclitaxol conjugate that targets lipoprotein receptor protein-1, a cell surface molecule overexpressed on solid tumor cells. This conjugate is under clinical assessment for treatment of advanced solid tumors, in particular in patients with brain metastases [Kurzrock, R. et al., Mol Canc Ther, 2012, 11, 308-316]. Potent luteinizing hormone releasing hormone (LHRH) antagonists, were used as targeting moieties for a variety of cancer drugs, including doxorubicin and its analogs, and studies on conjugates of [D-Lys6]-LHRH-DOX and [D-Lys6]-LHRH-2-pyrrolino-DOX showed increased efficacy of the drug as the LHRH analog maintained its highly targeted binding affinity while the drug retained its cytotoxic effects on the tumor cells [Schally, A. V. and Nagy, A., Eur J Endocrinol, 1999, 141, 1-14].
Another cell-surface receptor family, G protein-coupled somatostatin receptors (SSTRs), have drawn the attention of medicinal chemists as promising targets for TDD by conjugates based on SSTR specific peptide ligand conjugates [Sun, L. C. et al., Curr Drug Del, 2011, 8, 2-10]. The expression of SSTRs in peritumoral veins is a general phenomenon in blood vessels of many tumors [Reubi, J. C. et al., Eur J Nucl Med Mol Imaging, 2003, 30, 781-793].
The aberrant expression of SSTRs in various tumors and angiogenic tumor vessels, offers an additional opportunity for cancer patients to be treated with SST- or analog-based receptor-specific cancer therapy. After binding to their receptors, SST and its analogs are rapidly internalized into the cells and may even translocate to the cell nucleus. This may reduce the side effects of MDR often observed with traditional chemotherapy. Notably, due to the preferential expression of SSTR2 in many tumors and tumoral blood vessels when compared to other SSTR subtypes, most of these SST conjugates have been designed to target SSTR2-specific sites. Several delivery systems based on SST analogs have been reported. JF-10-81, a camptothecin-SSTR2 conjugate, was prepared by directly coupling camptothecin (CPT) to the N-terminus of an S—S bridged octapeptide SST analog via the cleavable carbamate group and a basic N-terminal linking motif [Sun, L. et al., Drug Deliv, 2004, 11, 231-238]. This conjugate had potent inhibitory activity against various human tumors in vivo, including neuroblastoma IMR32, pancreatic cancer CFPAC-1, pancreatic carcinoid BON, prostate cancer PC-3, leukemia MOLT-4, small cell lung cancer NCI-H69 and rat pancreatic cancer CA-20948 [Sun, L. et al., Clin Med Oncol, 2008, 2, 491-499]. Paclitaxel (PTX, taxol), which targets tubulin and leads to the inhibition of cell division, was conjugated to the N-terminal of the octapeptide SST analog octreotide [Huang, C. M. et al., Chem Biol, 2000, 7, 453-461]. This conjugate retained the cell-selective binding of octreotide and the biological activity of PTX, and appeared to be exclusively cytotoxic to breast cancer MCF-7 cells highly expressing SSTR2. The potent cytotoxin doxorubicin (DOX) was conjugated to SSTR2-specific octapeptide SST analog to produce a cytotoxic DOX-SST conjugate AN-238 [Engel, J. B. et al., Mol Pharm, 2007, 4, 652-658]. This anticancer drug conjugate displayed significant anti-tumor activities and reduced toxicity against various cancers such as ovarian, endometrial breast, prostate, pancreatic, renal cell cancers, hepatoma, melanoma, lymphoma, small cell lung cancer (SCLC) and glioblastoma [Schally, A. V. et al., Trends Endocrinol Metab, 2004, 15, 300-310; Schally, A. V. et al., Eur J Endocrinol, 1999, 141, 1-14.]. In addition, AN-238 was reported to overcome multi-drug resistance resulting from conventional chemotherapy [Enge, J. B. et al., Endocr Relat Cancer, 2005, 12, 999-1009].
The chemistry of carrier-drug attachment has received much attention. Main parameters include selection of a linker attachment site that retains carrier activity, linker length and composition, and the design of drug analogs for attachment to the linker. In an exemplary case of antibody-drug conjugates (ADC), two methods are now commonly used for conjugating drugs to antibodies: alkylation of reduced inter chain cysteine disulfides through a non-cleavable maleimido linker and acylation of lysine residues by cleavable linear amino acids. Cathepsin-cleavable linkers are also utilized (for example Val-Cit, or Phe-Lys) bound to self-emulative moiety PABA (p-aminobenzyl alcohol), enabling selective drug release in cancer cells. Spacers are usually essential extensions of the drug linkage and are responsible for avoiding the shielding of the active site of the antibody as well as improving solubility properties of ADCs (for example by the use of polyethylene glycol).
Carrier-drug conjugates have been successfully demonstrated and employed for the targeted delivery of drugs and toxins to receptor-positive murine leukemic cells. In particular, the use of multifunctional dendrone linkers that bear several covalently bound DNA alkylating chlorambucil (Leukeran) molecules to one peptide carrier have enhanced efficacy of growth inhibition of targeted cancer cells.
Ducry, L. et al., [Bioconjugate Chem., 2010, 21, pp. 5-13] present antibody-drug conjugates (ADCs) that combine the specificity of monoclonal antibodies (mAbs) with the potency of cytotoxic molecules.
U.S. Pat. No. 5,714,166 relates to a dendrimer coupled to at least one bioactive agent, particularly the agent being a biological response modifier. U.S. Pat. No. 5,830,986 provides a method for synthesizing a dendrimer based on polyethylene oxide for binding a biologically active molecule. U.S. Pat. No. 6,020,457 teaches dendritic polymers for drug delivery, containing a disulfide moiety in the core. U.S. Patent Application No. 2002/0071843 relates to a targeting therapeutic agent comprising a targeting entity which binds to a site of pathology, a linking factor, such as a dendrimer, and a therapeutic entity, the factor eventually binding additional materials. U.S. Patent Application No. 2003/0180250 provides a dendrimer complexed with an anti-inflammatory drug. WO 2004/019993 discloses a self-immolative dendrimer that releases many active moieties upon interacting with a single activating event. U.S. Patent Application No. 2004/0228831 describes a polymeric drug conjugate comprising one or more biologically active agents linked via an enzymatically cleavable linker, for targeting a diseased tissue.
WO 2008/047345 teaches a multifunctional platform for covalent binding of at least two different therapeutic or diagnostic agents and for their sequential release at a target site in a biological environment.
Gilad, Y et al. [Eur J Med Chem., 2014, 85, pp. 139-46] each an amino acid-based platform loaded with one or two drugs for conjugation to a peptide targeting moiety.
Additional background art include U.S. Pat. Nos. 8,703,114 and 9,050,370, U.S. Patent Application Nos. 20150017115 and 20140271483, and WO 2014/203189.
All documents cited herein are hereby incorporated by reference.